PROJECT SUMMARY/ABSTRACT Diabetes distress (DD) refers to the often hidden emotional burdens, stresses, and worries that result from managing a demanding, progressive, and chronic disease like type 1 diabetes (T1D). DD is highly prevalent, with approximately 42% of T1D adults manifesting elevated DD; is distinct from clinical depression; tends to be chronic, rather than episodic; and has been significantly associated with poor glycemic control and problematic self-care behavior. Systematic reviews suggest the development of effective interventions for DD have been impeded by: the majority of interventions not targeting DD directly, instead delivering various forms of diabetes education and disease-management, few studies being grounded in a theoretical framework that drives an intervention strategy; study designs that rarely allow for direct comparison of different approaches to reduce DD; relatively few studies focused on T1D, and no study to date that has explored different approaches to DD reduction in ways that directly maximize improvements in glycemic control. To address these problems we propose a 3-arm clinical trial with T1D adults that uses theoretically supported, evidenced-based interventions to test the added value of a program that targets DD directly through emotion regulation strategies (TunedIn) and a unified DD and disease management intervention (FixIt) to reduce DD and improve glycemic control, relative to a traditional education/disease management intervention (StreamLine). The primary outcome is HbA1c. We will explore mediating pathways linking changes in DD with changes in HbA1c over time. The effect of selective moderating variables on intervention effectiveness will be assessed. Intervention costs and stakeholder input will inform dissemination and future program implementation.